Charger Power Supply Amps

[awol]

I still haven't got this volts x amps / something thing yet.
I want to charge 2x 8ah 6s lipo batteries paralleled together on a turnigy 50w 5a charger, or even a new bigger one.
I will soon be ordering a power supply to hopefully up the charge rate so how do I work out the power supply in amp needed to charge them together at say 8.0a
The one I have is a 7a laptop style one (which is the style I will need to use) which gets too hot for comfort at a very slow charge rate.

 

[D8ve]

Volts x Amps = Watts or W/A= V
Or W/V=A your 50 watt charger with 6s (24)v will provide about 2amps and charge your 16AH of batteries in 8 hours ish.
To provide 8 A you need about a 200watt supply. 24x 8.

 

[awol]

Volts x Amps = Watts or W/A= V
Or W/V=A your 50 watt charger with 6s (24)v will provide about 2amps and charge your 16AH of batteries in 8 hours ish.
To provide 8 A you need about a 200watt supply. 24x 8.

I had to read that several times to get it (or not).
So the biggest power supply I might as well use on this 50w charger is 50w(charger)/24(6s)=2a(psu) ? But I'm sure my psu is 12v 6a (not got it with me)and gets very hot as if it's overworking.
This is where I get confused is that the power supply is 12v, and that doesn't seem come into it.
Also the charger being 50w 5a and you say I need 200w power supply, does that mean I would also need a bigger charger which does 200w ?

 

[Deleted member 4366]

Not quite right. There's two 16ah bricks, so it'll take twice as long to charge them before you can ride the bike. It's easier to deal in watt-hours. 16ah x 24v (approx) = 384 wh per brick = 768wh total divide by 50w to get hours = approximately 15 hours.

 

[D8ve]

Yes a bigger charger and power supply better to go for over 200watts if possible even if it costs a little extra.
The charger can have circuits to up the voltage and inefficiency,s here all add up to the excess heat generation.
I normally would suggest D8veh is more expert than me and listen to him as he has done this more often than me.
But do you have 2x 8 A batteries or 2x16A?

 

[awol]

2x 8a batteries.

 

[Deleted member 4366]

The time will be half then. Ithought it was those 16ah bricks that Hobbyking do.

 

[awol]

So at the moment my charger charging 6s(24v) at 2a uses 48watts which is it's max and so the 12v 6a(72w) power supply should easily cope with that? Even though it does get really hot.

 

[Geebee]

It depends on which charger, can you tell us the model?
If it us a 50w charger then to charge 6s batteries it has to step the 12v in up to (roughly) 24v so 24 x 2.2 amps = just over 50w.
So even if you supply a 20 amp 12v power supply it will not charge any faster if it is a 50w charger.
I have a 50w charger as well so the above is accurate in the real world, my 4s pack chages faster as it is (roughly) 16v at 3.2 amps = just over 50w as the lower charge voltage does not need to be as higher charge voltage.

For your usage an 80w charger would max out at around 3.33 amps charge current with 6.66 amps input from the power supply and would charge the 2 packs from flat in around 5 hours.

A 200w (expensive) charger would charge at 8.33 amps and require a power suply of at least 16,66 amps but would charge the 2 packs from flat in around 2 hours.

 

[awol]

My charger is called a turnigy and states 6s at 6a charging on it.
I've done an experiment and found my cheap 12v 6a psu causes the charger to alarm out at 6s 1.7a and above charge so have I been done with a rubbish psu?
I also borrowed a 15v 7a psu and the charger will only go up to 6s 2.3a charge but not above even if I set it up to 6.0a
How do those figures look?

 

[D8ve]

If it's a 50watt charger then about 2 amps max for 6s anyhow. How many watts is the charger rated at?

 

[awol]

It doesn't say on it how many watts the charger is, but from what I've learned here it works out to be 50w and if I buy a 15v 7a psu it will charge my battery at 2.3a from flat in about 7.5hrs.
and if I decide I need it quicker in the future I will upgrade the charger to maybe an 80w which the psu will still be ok with.
I also worked out my cheap 12v 6a psu must actually be a 12v 3a which is partly why I was struggling with all the calculations. Thanks all.

 

[mfj197]

Which exact Turnigy charger is it? It will have a model code or number on it somewhere. If it will actually charge 6S at 6 amps then it's certainly not a 50W charger, more like a 150W charger (25.2V * 6A).

Actually looking at their range is it something like this Turnigy Accucel-6? In which case yes, it is 6S, or 6 amps, but not both at the same time and it is rated at only 50W. That would make more sense from your observations. So you are currently running at the maximum capacity of your charger and power supply, so to charge quicker you would need to get more powerful versions of both.

Michael

 

[awol]

Which exact Turnigy charger is it? It will have a model code or number on it somewhere. If it will actually charge 6S at 6 amps then it's certainly not a 50W charger, more like a 150W charger (25.2V * 6A).

Actually looking at their range is it something like this Turnigy Accucel-6? In which case yes, it is 6S, or 6 amps, but not both at the same time and it is rated at only 50W. That would make more sense from your observations. So you are currently running at the maximum capacity of your charger and power supply, so to charge quicker you would need to get more powerful versions of both.

Michael

Yes it's that Accucel-6, I thought it was it was 6s at 6a and also thought my cheap 12v 6a charger was 72w but it must only be 3a 36w ish so I've learned how to work it all out now from this help.